How to mak ringtone for nokia sets

[MrKool]

I want to start a service to provide ringtones from short mp3 (avg 10 seconds )to nokia keypress format for nokia phone. But i do'nt know how to do this.
Anyone can guide me step by step how to make ringtone in keypress format. just like the format below.

--------------------------------------------------------------------
2*, 28, 2, 29, 6, 38, 4, 3, 2, 19, 3, (hold 2)8, 38, 29, 1, 2, 3, 49, 2888, 3999, (hold 2)8, 18, 6999**, 28*, 28, 2, 29, 6, 38, 4, 3, 2, 19, 3, (hold 2)8, 38, 29, 1, 2, 3, 49, 2888, 3999, (hold 2)8, 18, 6999**

tempo: 180 bpm
---------------------------------------------------------------------